My understanding is that a buff area makes the ball's transition smoother. The pattern has less volume at the end of it, so it tapers. If the pattern doesn't have this, the ball will see dry more suddenly, thus making the reaction more aggressive off the spot.
Make no assumptions on how to play this, but I'd start somewhere between 10-15 at the arrows out to 8 or so. With a medium ball, preferrably sanded.
Bookmarks